1. Field of the Invention
The present invention relates generally to a jumper structure and, in great detail, to a jumper structure suitable for being used in a precision apparatus a thickness of which is restricted, such as a watch.
2. Description of the Prior Art
It is well known in a watch or the like to use a jumper structure for rotating a date indicator for indicating a date having a date feeding finger engaged with teeth of the date indicator and having a jumping and restricting portion loaded by a spring and engaged with the teeth of the date indicator to stop rotation of the date indicator at every pitch of the teeth.
According to such a jumper structure, the jumping and restricting portion is thickly formed in order to make engagement between the jumping and restricting portion and the teeth of the date indicator difficult to disengage even when an impact occurs by dropping the watch. When the thick jumping and restricting portion is used, the jumping and restricting portion is formed by resin (plastic) in order to minimize mass (weight). Meanwhile, since the spring portion is always applied with a load an therefore, it is difficult to use a resin which is difficult to avoid a creep phenomenon owing to plastically flowing performance and a metal material is used as a material of the spring portion. As a result, typically, the jumper structure is provided as a composite structure constituted by mutually fixing and coupling the jumping and restricting portion made of a resin and the spring portion made of a metal.
However, according to such a composite structure, not only is part cost or fabrication cost likely to increase but also there is a concern that a dispersion is likely be to caused in a property of the composite structure.
Further, although there is known a constitution in which a jumping and restricting portion and a spring portion are integrally formed by a metal material having spring performance, when the jumping and restricting portion is thinned to minimize weight, there is a concern that engagement between the jumping and restricting portion and a teeth portion of a date indicator is liable to disengage.
Meanwhile, recently, there has been proposed to make a coil spring by molding a carbon nanofiber by a resin.